DE2600683C2 - Current limiting arrangement with a vacuum switch - Google Patents

Description

- that parallel to the contact pieces. (26, 28) the terminals of the vacuum switch (16) a capacitor (65) is arranged.

The invention relates to a current limiting arrangement with a vacuum switch according to the preamble of the main claim.

There is a need in the electrical industry for high speed switches as part of a current limiting arrangement. The need for such current limiting circuits arises from Fault currents that are becoming more and more noticeable in power networks. This in turn makes it necessary, in the case of better-working Shaiians or others Provide installations to limit such fault currents. The resulting demands were discussed in detail in an article published on the occasion of an IEEE symposium on current limiting devices in California on July 18, 1974 under the title // Current Limiting Devices - Need and Application "by C. A. Falcon et al. has been published.

jo There are already a large number of current limiting arrangements known and developed. Such a known current limiting arrangement is used a vacuum switch which is opened during the rise of the fault current from its peak value.

The arc current is then pulsed to zero by discharging a capacitor by the Discharge current is directed opposite to the fault current. This discharge current is transferred from the capacitor a triggered vacuum discharge *. », recke removed. The circuit through the vacuum switch is then switched to a current limiter, e.g. B. a resistor switched, which is parallel to the vacuum switch. This system has the disadvantage that two current pulse circuits are required for the two polarities of the light arc current. Another disadvantage will be seen in the fact that the capacitors of the pulse circuits are acted upon by the network potential and as a result which become very expensive in their construction.

It is also known to use a current limiting arrangement when a fault current is detected to operate quickly responding SFb gas pressure switch. By actuating this gas pressure switch, the current is transferred to a cross-sectional tube in which, When the magnetic field in the tube has come to rest, the current is either directed to a choke or a Resistance is switched. The three-stage power transmission facilities become a disadvantage of this system and the use of a cross-field tube respected, especially since such cross-country tubes are still under development.

It is also already known (US-PS 32 83 101). a magnetic field to a vacuum switch during opening the switch to / .ulcgen to activate the l.iehibo gene plasma on the inner electrode gap b'w. Kon ·

limit t> 5 cycle gap / u. With such an arrangement the current is interrupted at the zero crossing, d. H. at zero current and not before. There is no evidence whatsoever that such a facility could

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limiters can be used. The same goes for the Vacuum switch according to the preamble of claim 1, as it is known from US-PS 33 45 484 There a transverse magnetic field is applied to the switch with an independent power source when the Current has dropped to zero in order to prevent the switch from igniting again.

It is also known (US PS 37 16 685) to provide magnetic fields that are both parallel and radially perpendicular are aligned with the direction of current flow at the moment in which the circuit is broken takes place to initiate arc instability and thereby cause the arc Transitions to the partition walls surrounding the arc gap. A magnetic field takes place in use in the axial direction, which is greater than the effective field in the radial direction, in order to achieve the desired To cause arc displacement.

A vacuum switch with a magnetic field extending in the axial direction is disclosed in US Pat. No. 3,345,484 known. This field is controlled by the current in the switch itself, so that a strong Magnetic field occurs; this is intended to reduce the risk of re-ignition of the vacuum switch. One Magnetically highly permeable shielding prevents the creation of magnetic fields with small currents.

The use of magnetic plates for arc suppression is also known (US Pat 35 64 176 and 29 22 926), which are supposed to trigger an arc instability / to make it easier to extinguish the arc. However, no way has been shown how such plates can be subjected to current chopping in a vacuum switch can be used to limit the current.

DE-AS 11 91 461 describes a vacuum switch with a metallic ring-shaped electrode, which is attached in an insulated manner in the vicinity of the switch contacts; Its purpose is to maintain the stability of the arc between specially surface-treated parts increase the amount of confection.

A vacuum switch with one for interruption stretching parallel resistor is described in DE-AS 11 33 785: this resistor is when Opening the switch for a certain time activated via a sliding contact to prevent overvoltages. After the switch has been completely opened, which happens when the current passes through, it is not more effective and therefore no longer works in the sense of a current limitation.

There is also already the use of a vacuum arc known as a plasma source (journal Proceedings of IEEE, Volume 6ü. No. 8, 1962. Pulsed Metallic-Plasrna Generators «). The arc is formed on the surface of a depleted cathode, which can consist of an electrically conductive material. The plasma is made by an annular Anode in the form of a highly oriented conical bundle ejected at high speed. It One or more magnetic field coils can be used to adjust the impedance and alignment of the bundle to adjust. It should be noted that this plasma generator can be used as a switch for very large powers can be used. The pulsed metallic plasma generator uses fixed electrodes with a ring-shaped anode, which runs concentrically to the cathode ignition arrangement. The difficulty of such Institutions bJ'that that they relate to the arc polarity is very sensitive. which is particularly disadvantageous in AC circuits, and that the electrodes of the device are fixed so that they cannot be brought into contact with one another to complete the circuit.

The invention is based on the object of providing an arrangement according to the preamble of claim 1 to be trained so that after the arc has been extinguished in the vacuum switch, the current is switched off Circle is delimitable, being simple and safe

ίο Synchronization between opening the contacts of the vacuum switch and the flux density of the magnetic field then running across the switching path should be.

This object is achieved by the invention characterized in claim 1. Refinements of the invention are: characterized in the subclaims.

In operation, the vacuum switch described is within the first two milliseconds after the occurrence of a fault current in a heavy current network with high voltage activated. The contact pieces of the switch move very quickly with., an opening on a relatively large distance. Damping coils or other suitable devices may be required and be connected to the contact arrangement,

to ensure this rapid opening of the switch. As soon as the contacts of the switch are pulled apart far enough a transverse magnetic field is pulsed and applied to the arc allowed to act. Mechanical connections or electrical switches can be provided for this purpose, which first trigger the movement of the contact pieces and then immediately switch on the transverse magnetic field. This magnetic field causes a strong arc instability, so that this extinguishes and the Current to a circuit running parallel to it with current limiters arranged therein transforms. These current limiter devices can, for. B. from surge arresters, resistors. Throttle networks or the like. The arc instability can be further reduced by the provision of partitions enlarged in the area of the contact pieces and the use of tungsten as contact material since this contact material has a relatively high cathode inobility.

A major advantage of the switch described here is its ability to control the arc to extinguish under power; So there is no need to wait for the current to cross zero.

The desire for a relatively large opening range for the contact pieces it may be necessary to provide an axial magnetic field in order to avoid the Anode point formation during the opening of the contact pieces to delay. When this is the case, the axial magnetic field is just before reaching the largest Contact status switched off, which continues to increase the arc instability. The subsequent Applying the transverse magnetic field triggers the desired extinguishing of the arc.

Such vacuum switches with transverse magnetic fields can be used in series with other vacuum switches that do not have a transverse magnetic field to have. The arcs in the conventional switches are extinguished at the same time as the Arc in the with a transverse Ma-

b => switch provided with a gnetfeld, but the return voltage resulting from the forced zero crossing of the current is distributed to the arc gaps of the switches connected in series. This results in

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resistance to high voltages and ease of handling high voltages.

It can also be desirable for special applications to have capacitances in parallel with the switch contact pieces to switch. These capacitances also increase the arc instability and reduce the rate of rise of the recovery voltage after the zero crossing of the Arc current. The current interruption in the vacuum switch can result from the use of such parallel-connected Capacities benefit.

The vacuum switch according to the invention can be used both for direct current circuits and for alternating current circuits find application as a current limiter.

It is advantageous to use vacuum switches with pull-apart contacts, as these currents with different polarity. This eliminates the difficulties associated with

different polarity are effective. By using the transverse magnetic field for magnification the circuit breaker properties of a vacuum interrupter results in a device with which a current limitation can be made very quickly.

Embodiments of the invention are shown in figures. It shows

F i g. 1 shows a section through a vacuum switch with associated circuit parts;

FIG. 2 shows a section through a switch according to FIG. 1, which has an intermediate wall for enlargement the instability is provided;

Fig. 3 shows a current limiting circuit for high voltage using a vacuum switch as a current limiter, with a transverse magnetic field connected in series to further vacuum switches is:

Fig. 4 is a graphical representation of the to a vacuum switch applied pulsed and transverse magnetic field to extinguish an alternating current arc;

FIG. 5 is a graphic representation of the interruption of the direct arc current and the direct arc voltage depending on the transverse magnetic applied to the vacuum switch Field;

6 shows a circuit according to FIG. 1 using of damping coils and axial magnetic field coils.

The circuit 10 shown in Fig. 1 comprises a vacuum switch IG. which consists of a highly evacuated housing with an insulating jacket 18 made of glass or ceramic and two end caps 20 and 22, with which the insulating jacket 18 is closed at the two ends. Seals 24 are provided between the end caps 20 and 22 and the insulating jacket 18 in order to make the interior of the vacuum switch vacuum-tight. The pressure in the housing is less than 133 nbar during normal operation in order to ensure that the mean free path for electrons is greater than the possible breakdown distance inside the insulating jacket 18. Two electrodes or contact pieces 26 and 28 which can be displaced relative to one another are arranged within the insulating jacket 18. When the contact pieces 26 and 28 are separated, a gap is created in which an electric arc occurs when an electrical circuit is separated. The upper contact piece 26 is fastened in a stationary manner to a conductor rod 32. This conductor rod is rigid with the end cap 20 z. B. bound by welding or brazing. The lower contact piece 28 can be displaced along the longitudinal axis of the insulating jacket 18 together with the conductor rod 34. This displaceable ladder shaft 34 protrudes through an opening 36 in the end cap 22, as can be seen from FIG. 1. A metal bellows 38 is attached on the one hand to the electrode shaft 34 and on the other hand to the opening 36 and thus creates a seal in this area of the vacuum switch while the conductor rod 34 can be displaced evenly. Due to the flexibility of the metal bellows 38, the conductor rod K can be displaced, without affecting the vacuum inside the housing. With the lower end of the displaceable conductor bar 34 an actuating device (not shown) is connected which serves to bring the movable contact piece 28 to bear against the stationary contact piece 26 and to close the vacuum switch. This Uciäii iTiiniTCfinricHtiintT j-ollif in ri # * r I üuf * ^ pin dip hi * iiit * r contact pieces relatively far, z. B. about 2 cm, within a very short period of z. B. sth; Pull apart 1 millisecond. When the contact pieces 26 and 28 are separated, an arc 54 arises between the contact pieces. The arc vaporizes some contact material, which disperses in the form of material vapors and metal parts away from the light bulb gap 30 in the direction of the oil jacket 18. To the insulating jacket 18 from condensation of the Lichtbo

To protect the generated metal vapors and metal pieces, a tubular shielding 40 made of metal is provided, which is held in a suitable manner by the insulating jacket 18 and is preferably isolated from the end caps 20 and 22. From this shield 40 causes metal vapors and metal particles generated by the arc to be captured or condensed before they can reach the Isoliermantcl 18. In order to further prevent metal vapors or metal parts from bypassing the shielding 40 anyway to the insulating jacket 18, shielding caps 42 and 44 are provided which overlap at opposite ends of the metal shielding 4 over them. With the displaceable conductor rod 34 is also a cup-shaped shield 4 '.

connected, at least partially over the Metallbnlj 38 engages and prevents the metal bellows from arcing with the metal damper or metal particles are applied. The speed at which the arcing occurs

the resulting metal vapors are eliminated, determine the recovery properties of the circuit or de: Switch. If the vapors are not removed quickly enough, high equalizing voltages can be used again trigger the ignition, which causes the vacuum switch to fail.

There are also field coils 60 and 62 are provided generate a magnetic field running transversely to the arc path when excited. That behaves moderately long arc 54, which is in the vacuum

bO switch 16 is formed by a pulsating ma magnetic field made unstable by the Fcldspu len 60 and 62 transversely to the longitudinal axis of the arc: acts. This transverse magnetic field be has the effect that the arc current passes through zero

fa5 passes earlier than the normal Stromumpolunt corresponds to the zero crossing of the alternating current. An energy is generated when the field coils 60 and 62 are excited Supply 64 to the dishwasher via a switch 66

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connected. Since this excitation of the field coils takes place with the aid of an energy supply that is independent of the mains voltage, the magnet coils can be at any desired potential. This results in advantageous safety conditions and the possibility of using relatively cheap Niederspannmngskondensatoren for the energy supply 'corners 26 and 28 separated from each other and the arc 54 is extinguished. The current is called through a resistor 74. The strong magnetic field across / around the arc 54 forces the arc to be extinguished quickly. This high transverse field creates an arc instability by making the flow of current between the conical pieces 26 and 28 more difficult and by displacing the K jiihrwjonniinliι from Hfr KaihriHp ργ7ριιρι. w; is yu leads to a reduction in vapor and plasma in the anode area. If the strong transverse magnetic field is combined with a rapid separation of the contact pieces over a relatively large distance, a sirom-limiting switch results. The current interruption is brought about within the first two milliseconds of the fault current request! When the vacuum switch 16 is opened. The contact pieces of the switch 16 are brought when opening to a distance that is relatively large and z. B. can be 2 cm. This should take place very quickly and can therefore make vaccination coils necessary at the contact gaps 26 and 28 or at the conductor bars 32 and 34. Although only the contact piece 28 is shown movable in FIG. 1, a switch can of course also be constructed so that the two contact pieces 26 and 28 can be displaced with respect to the insulating jacket 18 in order to effect a rapid separation of the contact pieces. If the contact pieces 26 and 28 according to FIG. 1 are relatively far apart, the magnetic field will act on the arc 54 in a pulsed manner. As already mentioned, this transverse magnetic field triggers an arc instability. The arc 54 eriischt some of this instability, so that the current is now conducted via the resistor 74 lying parallel to it, which acts as a current limiter. This current limiter can consist of a conventional resistor, but it is also possible to use a surge arrester, a choke chain or the like in its place. The arc instability can be further increased by using suitable materials for the contact pieces 26 and 28, tungsten having proven to be particularly advantageous since this material has a relatively high cathode point mobility and is able to interrupt relatively high currents.

In Fig. 2, a switch 16 is shown with a Partition 48 is provided in the area of the arc. This partition supports the enlargement the arc instability.

The desire to pull the contact pieces 26 and 28 apart relatively far, the use make an axial magnetic field necessary to delay the anode point formation until the Koniaktslücke are completely separate. This axial magnetic field is switched off when the contact pieces are completely stretched out, causing a tendency to create an arc instability. As soon as the axial magnetic field is switched off, the Field coils 60 and 62 energized to allow the transverse magnetic field to act on the arc 54.

In the embodiment of the invention according to FIG. 3 can control the transverse magnetic field during the Circuit interruption are applied, with one or more vacuum switches 14 in series in the circuit are switched. The extinguishing of the arc in the vacuum circuit breaker 16 can in the above

ίο described way by putting on the transverse Magnetic field take place. The arcs in the circuit breakers 14 extinguish at the same instant like arc 54 when the transverse magnetic field is applied to switch 16. However, it works the recovery voltage after the forced zero current at the series connection of the arc gaps Switches 14 and 16. This arrangement is desirable for high voltage current limiters. If the Is suppressed through the .Schalter 14 and 16 flowing current, a current flow through the parallel to it Circuit with the current limiter device 74 forced.

In Fig. 6 is a current limiting vacuum switch shown, the damping coils 81 and field coils 83 for an axial magnetic field. The damping coils 81 and the field coils 83 can, as shown, be connected in series. Furthermore, the energy supply from the axial field coils 83 to the field coils 60 and 62 for generating the transverse magnetic field be switched when the vacuum switch 16 is opened. This is done with the help of a switch, which is actuated by moving the conductor bar 34. The over the various coils 60, 62,81 and 83 Current flowing can also be from the main circuit

be derived. While the switch is opening 16 according to FIG. 6, a current flows through the damping coils 81, so that opposing magnetic fields in these are generated, which move the two coils 81 apart very quickly. This allows the Open switch 16 very quickly. To hold the contact piece 28 in the open position, a catch can or pawl can be provided, which is effective in the outermost position of the guide rod or Koniaktsiückes.

According to FIG. 3 can be parallel to the contact pieces

• 5 26 and 28 a capacitor 65 must be connected. This Capacitor 65 improves arc instability and reduces the rise in recovery voltage, which follows the zero current of the arc. The forced break in switch 16 benefits from

so the use of the parallel capacitor. When a peak current of, for example, 1.65 kA is interrupted in the arc with a frequency of 60 Hz, a capacitor with a capacity of 14 μ? parallel to the switch the overvoltage to about 33 kV.

Experiments have shown the usefulness of using transverse magnetic fields for current limiting confirmed. A conventional switch about three inches in diameter was used for an experiment arranged between two field coils for generating a transverse magnetic field. Each of these field coils had a diameter of about 15 cm and 50 turns. When energizing these coils was the behavior of the arc current and the arc voltage are recorded. From the representation according to 4 one can see that when creating a pulsed magnetic field a very strong arc instability and the arc very quickly

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went out.

In Fig. 5 is the influence of a pulsed magnetic field on a DC arc current of about 800 amperes shown, which was set at a contact distance of about 1.27 cm, with a charged condensa- ■> tor was discharged via the field coils for the transverse magnetic field. You can see that the Arcing stray. almost instantly with mooring of the magnetic field is interrupted. Tests with larger currents have shown that the Liclitbogenstrom can be brought to zero in less than a millisecond after applying the field. This demonstration shows that the vacuum switch, on which a transverse magnetic field acts, is an essential one Is part of the current limiting arrangement. A large distance between the contact pieces and a high pulsed one Field cause an arcing instability with currents in high voltage networks with several 1000 Arnnrrp.

$ For this purpose 3 sheets of drawings

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50

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Claims (5)

26 OO 683 claims: 1. Flow limitation arrangement with a vacuum switch containing a highly evacuated tubular housing, two in the axial direction of the tubular Housing arranged contact pieces, of which at least one in the housing under Using a bellows is slidably mounted, as well as at least one laterally outside the housing at the level of the contact pieces from a separate power source via a switch powered magnetic field coil, from which a magnetic field running transversely to the arc axis with a magnetic field pulse that occurs when the magnetizing current is switched on can be generated, characterized, - That the switch (66) provided in the circuit of the at least one magnetic coil (60, 62) between this and the feeding power source (64) when the vacuum switch (16) is switched off only after the pair of contact pieces (26, 28) have been separated via a mechanical connection with the displaceable contact piece (28) closable i. ^c t. and that the current flowing in the circuit to be disconnected after the magnetic field pulse and the resulting arc extinction is carried out by a current which is electrically parallel to the pair of contact pieces; Enzende impedance (74) is feasible. 2. Current limiting arrangement according to claim 1, characterized in that - That the tubular housing (18, 20, 22) of the Vacuum switch (16) in the area of the arc path (54) with a central hole having intermediate wall (48) is provided (Fig-2). 3. Current limiting arrangement according to claim 1 or 2, characterized in that - That in the area of the movable contact piece (28) carrying the conductor bar (34) a Kampe or latch is provided, which lifts the conductor bar in the lifted from the fixed contact piece Holds the position of the movable contact piece (28), - and that in the circuit of the magnetic field coils (60, 62) arranged switch (66) is a changeover switch, via which first actuating coils (81) for opening the contact piece pair (26, 28) and then the magnetic field coils (60, 62) for the formation of the transverse pulse-shaped magnetic field can be switched on. 4. Current limiting arrangement according to claim 3, characterized in that. - <Jaß on the tubular housing (18. 20, 22) of the Vacuum switch (16) also two electrically connected to the actuation spuien (81) axial magnetic field coils (83) are provided with which a parallel to the arc (54) running magnetic field can be generated. 5. Current limiting arrangement according to one of the preceding claims, characterized in that